1. Technical Field
The present invention relates to a technique of ejecting liquid such as ink.
2. Related Art
From the related art, a liquid ejecting technique is suggested which ejects liquid in a pressure chamber from nozzles by varying the pressure of liquid in the pressure chamber by a pressure generating element such as a piezoelectric element and a heating element. In an ink jet type liquid ejecting head (a recording head) to which the liquid ejecting technique is applied, ink in the pressure chamber is ejected from the nozzles by selectively supplying a plurality of ejection pulses placed for each period (a printing cycle) of a driving signal to the pressure generating element. For example, as shown in (A) in FIG. 15, JP-A-2003-251807 discloses a technique which adjusts an electric potential range of each ejection pulse DP to the driving signal COM in which a plurality of ejection pulses DP (DP1, DP2, and DP3) ejecting inks of different weights is placed in the printing cycle TP.
In a technique of JP-A-2003-251807, an ejection pulse DP1 and an ejection pulse DP3 become a predetermined electric potential Vm in a starting end and a terminal end, and an ejection pulse DP2 becomes a ground electric potential GND in the starting end and the terminal end are arranged in the printing cycle TP. The ejection pulse DP2 is situated between the ejection pulse DP1 and the ejection pulse DP3. Furthermore, a preparation wave form DP0 to be changed from the electric potential Vm to the ground electric potential GND is placed ahead of the ejection pulse DP1, and a return wave form DP4 to be changed from the ground electric potential GND to the electric potential Vm is placed behind the ejection pulse DP3. When supplying the ejection pulse DP2 to the piezoelectric element, as shown in (B) in FIG. 15, the preparation wave form DP0 and the return wave form DP4 are also selected. When supplying the ejection pulse DP1 or the ejection pulse DP3 to the piezoelectric element, the preparation wave form DP0 and the return wave form DP4 are not selected. According to the configuration as above, it is possible to reduce the highest electric potential (the highest electric potential of the ejection pulse DP2) of the driving signal.
However, in a configuration of JP-A-2003-251807 in which the preparation wave form DP0 placed at the beginning of the printing cycle TP and the return wave form DP4 placed at the end of the printing cycle TP are selected together with the ejection pulse DP2, there are various restrictions in the selection of the wave form of the ejection pulse DP2 and each ejection pulse. For example, since the ejection pulse DP2 is based on the ground electric potential GND, the wave form is restricted to a shape which compresses the liquid in the pressure chamber once and decompresses the liquid after the compression. Furthermore, as shown in (B) in FIG. 15, since the preparation wave form DP0 and the return wave form DP4 are connected to the ejection pulse DP2 when selecting the ejection pulse DP2, there is a restriction that it is difficult to select the ejection pulse DP1 between the ejection pulse DP2 and the preparation wave form DP0 and the ejection pulse DP3 between the ejection pulse DP2 and the return wave form DP4 together with the ejection pulse DP2 in one printing cycle TP.